Viper wrote:QR_BBPOST Most newer model bilge pumps have check valves in them now to prevent that and back flow of what's left in the line after the pump shuts off.
Interesting.
Sure hope these new type pumps are better designed than the old cheaper versions, as they would need to open a check valve against a head of water.....that would take some more power than the older centrifugal designs that would just spin and heat up..... IMO.
Viper wrote:QR_BBPOST Most newer model bilge pumps have check valves in them now to prevent that and back flow of what's left in the line after the pump shuts off.
Interesting.
Sure hope these new type pumps are better designed than the old cheaper versions, as they would need to open a check valve against a head of water.....that would take some more power than the older centrifugal designs that would just spin and heat up..... IMO.
The biggest issue is when they get a bit of air trapped in them, then the impeller spins in air and doesn't develop any pressure. Drilling a small hole above the impeller will allow it to expel the air, but that hole (along with the check valve) severely cuts into the overall capacity of the pump. Add in some corrugated hose and a couple feet of head, and I'd bet a "2000GPH pump" can't actually pump more than 500GPH.
That kind of pump is fine for the nuisance bilge water, but I'd want a real "emergency bilge pump" right near it that has no check valves and a nice direct line overboard that would get rid of a lot of water in a hurry if you ever really needed it.
I haven't run into any issues with these pumps yet. The new designs come with anti airlock impellers designed to overcome air lock issues. They're just your typical bilge pumps with some mods. They have removable discharge fittings that allow you to insert or remove a check valve which is usually a duckbill similar to what you'd find in a shower sump, you can choose to have it in place or remove it. I think manufacturers are moving to this design for a couple of reasons; back flow prevention and safety to prevent seawater from getting in.
Viper wrote:QR_BBPOST They have removable discharge fittings that allow you to insert or remove a check valve which is usually a duckbill similar to what you'd find in a shower sump, you can choose to have it in place or remove it.
I like the sound of that, maybe the duckbill type design would be easier to get flowing than if it was a flap/door style.
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